The present invention relates to generator rotors, such as multi-pole generator rotors suitable for high speed applications.
Feasibility investigations suggest that power generators for aircraft and spacecraft may be constructed using highly efficient magnetic bearings. However, these same investigations suggest that weight effective designs can be achieved only with very high speed applications. Typical power generators, such as power generators found in aircraft, operate in the range of 24,000 rpm, and typically employ the pole configuration illustrated in FIG. 8 of the drawings. One problem encountered by the typical configuration shown is that at high rpm""s the resulting high centrifugal forces causes a radially outward displacement of the end-turns of the winding. This outward displacement causes the rotor to go out of balance and also creates the potential for field failure. Moreover, the sharp turns encountered by the wire on the region of the pole tip limits the gauge of wire that may be employed. Thus, it would be desirable to develop an improved winding system and an improved rotor design which would be operable at high speeds.
A six pole generator construction having an odd number of pole pairs constructed according to the teachings of the present invention will have a design speed of 50,000 rpm with an overspeed in the range of 55,000 rpm.
According to a first aspect of the invention, a multi-pole generator rotor comprises a rotor body including a central portion having a generally cylindrical outer surface. The outer surface includes three pairs of diametrically opposed slots extending along a length of the central portion, with each of the slots being sized to receive therein a plurality of wires. Each of the slots further includes a pair of opposed retaining flanges. A plurality of retaining members are sized for insertion into a corresponding one of the slots, with each retaining member engaging the opposed retaining flanges of its corresponding slot. The retaining members thereby retain the wires disposed in each slot against radially outward displacement.
In further accordance with a first aspect of the invention, the rotor body is rotatably mounted to a generator housing, and a continuous wire winding is wound upon the rotor body such that a plurality of wire sections is disposed in each of the slots. The rotor body includes a pair of ends connected by a central axis, and the wire winding includes a plurality of end portions adjacent each of the rotor body ends. Each of the wire winding end portions crosses the rotor body central axis, and an end support mounted to each of the rotor body ends supports the adjacent wire end portions. Preferably, the end supports include a plurality of aligning prongs, such as six aligning prongs. Still preferably, a cap member is mounted to each of the rotor body ends, with each of the cap members engaging an adjacent end support.
Preferably, each cap member also engages the end portions of the adjacent retaining members, thereby preventing longitudinal movement or displacement of the retaining members.
Preferably, the rotor body is mounted to a shaft, which shaft is rotatably mounted within a generator housing. Each of the cap members may include three intersecting grooves, with each of the grooves being sized to overlie an adjacent wire end portion. Each of the slot retaining flanges may include an angled surface, and each of the retaining members includes a wedge shaped edge. Each wedge shaped edge is sized to engage an adjacent angled surface, thereby securing each retaining member against radially outward displacement.
In accordance with a second aspect of the invention, a multi-pole generator rotor for receiving a continuous wire winding comprises a rotor body having a generally cylindrical central portion, with the central portion including a plurality of slots extending along the length thereof. Each of the slots is sized to receive a portion of the wire winding. Each of the slots further includes a pair of longitudinally extending edge portions, with each of the edge portions defining a retaining flange. A plurality of retaining members are provided, with each retaining member being sized for insertion in a corresponding one of the slots. Each of the retaining members includes a pair of edges sized to engage the edge portions of its corresponding slot. Thus, the wire winding portion disposed in each slot is held in a fixed position by the corresponding retaining member.
In accordance with another aspect of the invention, a multi-pole generator rotor comprises a rotor body having a generally cylindrical central portion, with the central portion including six slots extending along the length thereof. Each of the slots includes a pair of longitudinally extending edge portions, with each of the edge portions defining a retaining flange. A continuous wire winding is wound about the rotor body and defines three pole pairs, with each of the pole pairs engaging diametrically opposite slots. Six retaining members are provided, with each of the retaining members being sized for insertion in a corresponding one of the slots. Each of the retaining members includes a pair of edges sized to engage the adjacent retaining flanges. Accordingly, a portion of each coil disposed in each of the slots is held in a fixed position by the corresponding retaining member.
In accordance with a still further aspect of the invention, a multi-pole generator rotor comprises a rotor body including a central portion having a generally cylindrical outer surface. The outer surface includes at least one pair of diametrically opposed slots extending along a length of the central portion, with each of the slots being sized to receive therein a plurality of wires. Each of the slots further includes a pair of opposed retaining flanges. A plurality of retaining members are sized for insertion into a corresponding one of the slots, with each retaining member engaging the opposed retaining flanges of its corresponding slot. The retaining members thereby retain the wires disposed in each slot against radially outward displacement. Preferably, the rotor body outer surface may have an odd number of slot pairs.
In accordance with yet another aspect of the invention, a method of forming a multi-pole generator rotor comprises the steps of providing a rotor body having a cylindrical central portion and a plurality of diametrically opposed slot pairs defined in the central portion, with each of the slots in each slot pair extending along the length of the central portion. A first coil is formed by repeatedly winding a wire through a first of the plurality of slot pairs, a second coil is formed by repeatedly winding a wire through a second of the plurality of slot pairs, and a third coil is formed by repeatedly winding a wire through a third slot pair. A retaining member is inserted longitudinally into each of the slots.
Preferably, an end cap is secured to opposite ends of the rotor body. Further, each of the coils includes opposing end portions, and a coil support is inserted between each of the end caps and the adjacent coil end portions. Still preferably, opposing end portions of each of the coils are supported during winding. Each of the retaining members may be secured against longitudinal movement, such as by the end cap. The end cap is preferably sized to receive the adjacent coil end portions. Support for the rotor body and the end caps may be provided by shrink forming a retaining sleeve about the rotor body.
Additional features and advantages of the present invention will become readily apparent to those skilled in the art upon reading the following detailed description.